Gasses for inhalation are provided to medical patients under at least two totally different conditions. Anesthesiology gasses are applied during surgery, either through a mask, or through an endotracheal tube. Oxygen or a mixture of air and oxygen is supplied to a patient when the patient has trouble breathing on his own. In either case it is imperative that the pressure of the gasses supplied to the patient be within a certain range, neither too low nor too high.